Spawn Chunk issue

Command blocks are executed in "lazy chunks" but those are not necessarily the same as the spawn region chunks.
_{Edit: That's nonsense, see} @unknown_{'s excellent explanation.}

Anyway, not a bug.

When the spawn chunks "unload" after 60 seconds, any entities (including iron golems) and tile entities will stop being sent update ticks. However, not all tile entities rely on update ticks to work, which includes command blocks.

These are the following tile entities that have an update function called (1.8.8): Chest, MobSpawner, BrewingStand, Beacon, Piston, MobSpawner, Hopper, Furnace, EnderChest, EnchantmentTable, DaylightDetector.

All of those tile entities will not receive an update tick after the 1200 tick rule. This also explains why hopper clocks will stop functioning.

Then there's the remainder: CommandBlock, Skull, Banner, Comparator, Dispenser, Dropper, FlowerPot, Noteblock, Signs

Those tile entities do not follow that rule and have differing update mechanics. So for example, even though a comparator is a tile entity, comparator clocks will still function after the 1200 ticks because it doesn't follow that rule.

A village will still produce iron golems, but because the iron golems aren't sent update ticks, they will not be transported to a killing chamber. This mechanic is very likely to reduce server strain if no players are going to be in the overworld to use these entities/tile entities.

Thanks a lot for your answer, so if I correctly anderstand the iron golem can spawn but they are not load in the world if no one is connected this can explain why when I connect I can see at this moment one golem is gonna die in the killing chamber.

But before in previous patch, this mechanic was working no ? We were disconnected and iron golem was working ? What can I do to have iron golem even if I am disconnected ?

Wow, not a bug so mojang intentionnally broke a fairly important survival mechanic, without any form of communication ? That's really terrible. Fuck 1.9

1. this most likely always has been this way, as stated by @unknown before

These are the following tile entities that have an update function called (1.8.8)

this works the same way in 1.8.8
2. watch your language!

"That's your issue." Do you understand what I'm saying (I can understand if not, im not a native speaker at all). THAT WORKED IN 1.8.8 !! 5 minutes in the nether, back in the overworld, boom ! No more Item. U must not be interested, but people built a TON of machines relying on golems moving on water streams, hopper clocks, designed to work in the spawn chunks with NO PLAYER on the overworld. And THAT WORKED.

Um... this is a perfectly legitimate issue. It isn't invalid at all. Everything Jean and Alexandre has said is correct. Firing items through a nether portal to keep them loaded should work from all information Mojang has given us. And, it does work, but only for tile entities(for example, hopper clocks will work if this is done every 10 seconds or so). However, it does not send ticks to other entities, such as iron golems. While this may have been removed as a performance feature, there was no communication from Mojang that this was done. This bug should be either acknowledged as what it is, a bug, or we should receive public clarification from Mojang that this is an intended change in 1.9.

@@unknown What the others have said is incorrect, and what you have said is incorrect and proves itself false. If shooting an item into a nether portal kept only tile entities loaded, then the item entity couldn't be shot into a nether portal because it's not being ticked for physics (and thus couldn't keep tile entities loaded).

Internally, there is a 15-second timer that decreases when no players are in the overworld. If an entity travels through a portal to or from the overworld, that timer is reset. When that time reaches 0, then entities and tile entities won't be sent update ticks. There is nothing else that controls what is loaded or not loaded. Shooting an entity through a nether portal does not change how the spawn chunks function, just that they will continue functioning.

@Skylinerw That is a fair point, however, it seems as if only the item has physics being processed. Iron farms and the like don't work, even with the dispenser firing items into the portal. This doesn't make any sense, as if the item physics are being processed, iron golem physics and village spawning mechanics should work, as they should be being sent update ticks. This, however, doesn't seem to to be the case in 1.9 and 1.10.

Nevermind, I've done more research and experimenting, and it seems to be a more specific issue with iron golems. Sorry!